Look, it's really simple. If it was genetics, I thing you would all have to agree it's a recessive gene that causes it, 'cause the majority are hetero, not gay. Over the centuries, since gays would reproduce less, the occurance of the recessive gene would decrease, not increase, because the "pool" of recessive genes would decrease.
Increases occur only when it becomes more socially acceptable, similar to increases in out of wedlock births: no shame, less of a social taboo, occurences increase.
Many studies, NO genetic link found.